UBUNTU-CVE-2026-40203 (CVE-2026-40203)
Vulnerability from osv_ubuntu – Published: 2026-08-28 00:00 – Updated: 2026-09-02 16:15 – Source website
VLAI
Details
When IMAP compression is enabled, the same compression state is reused across responses in a session, so response sizes depend on both attacker-supplied mail and other mail in the same mailbox. An attacker that can send mail to a user and can also observe the sizes of that user's IMAP traffic can confirm whether the body of a small message matches a guessed text. Recovery of arbitrary unknown content was not demonstrated, but the attack can disclose whether a secret-like message body matches a candidate. Disable IMAP compression. Update to non-vulnerable version. No publicly available exploits are known.
Severity
N/A (UNKNOWN)
References
| URL | Type | |
|---|---|---|
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-core",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
},
{
"binary_name": "mail-stack-delivery",
"binary_version": "1:2.2.9-1ubuntu2.6+esm4"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:14.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.2.9-1ubuntu2.6+esm4?arch=source\u0026distro=esm-infra-legacy/trusty"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.1.7-7ubuntu3",
"1:2.2.9-1ubuntu1",
"1:2.2.9-1ubuntu2",
"1:2.2.9-1ubuntu2.1",
"1:2.2.9-1ubuntu2.3",
"1:2.2.9-1ubuntu2.4",
"1:2.2.9-1ubuntu2.5",
"1:2.2.9-1ubuntu2.6",
"1:2.2.9-1ubuntu2.6+esm1",
"1:2.2.9-1ubuntu2.6+esm2",
"1:2.2.9-1ubuntu2.6+esm3",
"1:2.2.9-1ubuntu2.6+esm4"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-core",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-lucene",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.2.22-1ubuntu2.14"
},
{
"binary_name": "mail-stack-delivery",
"binary_version": "1:2.2.22-1ubuntu2.14"
}
]
},
"package": {
"ecosystem": "Ubuntu:16.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.2.22-1ubuntu2.14?arch=source\u0026distro=xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.2.18-2ubuntu2",
"1:2.2.22-1ubuntu1",
"1:2.2.22-1ubuntu2",
"1:2.2.22-1ubuntu2.1",
"1:2.2.22-1ubuntu2.2",
"1:2.2.22-1ubuntu2.3",
"1:2.2.22-1ubuntu2.4",
"1:2.2.22-1ubuntu2.6",
"1:2.2.22-1ubuntu2.7",
"1:2.2.22-1ubuntu2.8",
"1:2.2.22-1ubuntu2.9",
"1:2.2.22-1ubuntu2.10",
"1:2.2.22-1ubuntu2.11",
"1:2.2.22-1ubuntu2.12",
"1:2.2.22-1ubuntu2.13",
"1:2.2.22-1ubuntu2.14"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-core",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
},
{
"binary_name": "mail-stack-delivery",
"binary_version": "1:2.2.33.2-1ubuntu4.8"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.2.33.2-1ubuntu4.8?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.2.27-3ubuntu1",
"1:2.2.33.2-1ubuntu1",
"1:2.2.33.2-1ubuntu2",
"1:2.2.33.2-1ubuntu3",
"1:2.2.33.2-1ubuntu4",
"1:2.2.33.2-1ubuntu4.1",
"1:2.2.33.2-1ubuntu4.2",
"1:2.2.33.2-1ubuntu4.3",
"1:2.2.33.2-1ubuntu4.4",
"1:2.2.33.2-1ubuntu4.5",
"1:2.2.33.2-1ubuntu4.6",
"1:2.2.33.2-1ubuntu4.7",
"1:2.2.33.2-1ubuntu4.8"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-auth-lua",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-core",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-lucene",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "dovecot-submissiond",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
},
{
"binary_name": "mail-stack-delivery",
"binary_version": "1:2.3.7.2-1ubuntu3.7"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.3.7.2-1ubuntu3.7?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.3.4.1-5ubuntu3",
"1:2.3.7.2-1ubuntu1",
"1:2.3.7.2-1ubuntu2",
"1:2.3.7.2-1ubuntu3",
"1:2.3.7.2-1ubuntu3.1",
"1:2.3.7.2-1ubuntu3.2",
"1:2.3.7.2-1ubuntu3.3",
"1:2.3.7.2-1ubuntu3.4",
"1:2.3.7.2-1ubuntu3.5",
"1:2.3.7.2-1ubuntu3.6",
"1:2.3.7.2-1ubuntu3.7"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-auth-lua",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-core",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-lucene",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
},
{
"binary_name": "dovecot-submissiond",
"binary_version": "1:2.3.16+dfsg1-3ubuntu2.9"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.3.16+dfsg1-3ubuntu2.9?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.3.13+dfsg1-1ubuntu3",
"1:2.3.16+dfsg1-3ubuntu1",
"1:2.3.16+dfsg1-3ubuntu2",
"1:2.3.16+dfsg1-3ubuntu2.1",
"1:2.3.16+dfsg1-3ubuntu2.2",
"1:2.3.16+dfsg1-3ubuntu2.4",
"1:2.3.16+dfsg1-3ubuntu2.6",
"1:2.3.16+dfsg1-3ubuntu2.7",
"1:2.3.16+dfsg1-3ubuntu2.8",
"1:2.3.16+dfsg1-3ubuntu2.9"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-auth-lua",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-core",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
},
{
"binary_name": "dovecot-submissiond",
"binary_version": "1:2.3.21+dfsg1-2ubuntu6.5"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.3.21+dfsg1-2ubuntu6.5?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.3.20+dfsg1-1ubuntu3",
"1:2.3.21+dfsg1-2ubuntu1",
"1:2.3.21+dfsg1-2ubuntu2",
"1:2.3.21+dfsg1-2ubuntu4",
"1:2.3.21+dfsg1-2ubuntu5",
"1:2.3.21+dfsg1-2ubuntu6",
"1:2.3.21+dfsg1-2ubuntu6.1",
"1:2.3.21+dfsg1-2ubuntu6.2",
"1:2.3.21+dfsg1-2ubuntu6.3",
"1:2.3.21+dfsg1-2ubuntu6.4",
"1:2.3.21+dfsg1-2ubuntu6.5"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "dovecot-auth-lua",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-core",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-flatcurve",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-gssapi",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-imapd",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-ldap",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-lmtpd",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-managesieved",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-mysql",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-pgsql",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-pop3d",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-sieve",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-solr",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-sqlite",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
},
{
"binary_name": "dovecot-submissiond",
"binary_version": "1:2.4.2+dfsg1-3ubuntu2.1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "dovecot",
"purl": "pkg:deb/ubuntu/dovecot@1:2.4.2+dfsg1-3ubuntu2.1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1:2.4.1+dfsg1-5ubuntu4",
"1:2.4.1+dfsg1-5ubuntu5",
"1:2.4.2+dfsg1-3ubuntu1",
"1:2.4.2+dfsg1-3ubuntu2",
"1:2.4.2+dfsg1-3ubuntu2.1"
]
}
],
"aliases": [],
"details": "When IMAP compression is enabled, the same compression state is reused across responses in a session, so response sizes depend on both attacker-supplied mail and other mail in the same mailbox. An attacker that can send mail to a user and can also observe the sizes of that user\u0027s IMAP traffic can confirm whether the body of a small message matches a guessed text. Recovery of arbitrary unknown content was not demonstrated, but the attack can disclose whether a secret-like message body matches a candidate. Disable IMAP compression. Update to non-vulnerable version. No publicly available exploits are known.",
"id": "UBUNTU-CVE-2026-40203",
"modified": "2026-09-02T16:15:05Z",
"published": "2026-08-28T00:00:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-40203"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-40203"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-40203"
]
}
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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